Heat exchanger with baffle securing means



United States Patent 3 437,133 HEAT EXCHANGERLZEEITHSBAFFLE SECURING A Russell H. Bullard, 118 Hawthorne Drive, Wilmington, N.C. 28401 Filed Mar. 23, 1967, Ser. No. 625,400 Int. 'Cl. F281? 1/10 US. Cl. 165-149 3 Claims ABSTRACT OF THE DISCLOSURE Summary Under the invention a rectangular framework is formed by a pair of longitudinal tube sheets and interconnecting perpendicular batlle sheets. The baflle sheets are provided with flanges which are turned onto the outside faces of the tube sheets so that suitable openings in said flanges fit over selected ones of the tube sheet fluid tube openings. Final assembly may be performed in a one-step process which involves running a tube-expander mandrel through each fluid tube. Mechanical expansion of the tubes automatically locks the baflle sheet flanges to the selected tubes, thus eliminating the need for screws, rivets, or other separate fastener devices. Improvement resides in lower assembly cost, higher strength connections, and greater rigidity of the framework.

The drawings FIG. 1 is a front elevational view of a heat exchanger and forming apparatus embodying the present invention.

FIG. 2 is a right end elevational view of the FIG. 1 structure.

FIG. 3 is an enlarged sectional view taken on line 33 in FIG. 2.

FIG. 4 is a sectional view taken on line 44 in FIGS. 1 and 3.

FIG. 5 is an enlarged sectional view taken on line 55 in FIG. 1.

The drawings in greater detail FIG. 1 shows a partially formed heat exchanger comprising a rigid framework 12, fluid tubm i14, and heat exchange fins L16. Framework 12- is made up of two tube sheets 18 and 20, each of right angle cross section, and two connecting baflle sheets 22 and 24, also of right angle cross section. Each tube sheet 1 8 or includes an apertured leg 26 for receiving the ends of tubes 14 and a second leg 28 provided with suitable openings 30 for mounting the heat exchanger in place on a suitable duct or unit structure (not shown). Each bafile sheet 22 or 24 includes a main leg portion 32 and a rigidifying leg 34 '(see FIG. 5). The opposite end of each baflle sheet are turned inwardly to provide flanges or tabs 36. As shown best in FIG. 1, the two baflle sheets are arranged so that flanges 36 thereof overlap wall portions 26 of the tube sheets 18 and 20.

In the illustrated heat exchanger the tubes 14 are formed as U-tubes comprised of straight portions 41 and return bend portions 43. This provides two rows of tubes having connected lower ends and open upper ends, said upper ends being subsequently connectable to suitable headers, return bends, distributors or other fluid line connectors (not shown) to provide a complete heat exchanger.

Fluid tubes 14 extend through apertures 44 in the tube sheets; additionally the two endmost fluid tubes extend through openings 46 in flange portions 38 of the bafiie sheets. By this arrangement the tubes serve as mechanical connections between the tube sheets and baflie sheets.

In assembling the heat exchanger components together the tubes are preferably positioned with their end portions 43 abutting against a stationary contoured support or nest 40, as shown in FIG. 2. The plate type fins 16 are stacked within the defined framework 12 with their collars 42 loosely encircling the tubes. Thereafter tubeexpander mandrels 48 are moved downwardly into the non-supported or free ends of the tubes by a mechanical press or other power device, not shown. Preferably the mandrels are operated together as a bank.

As each mandrel begins to move through the tube it initially forces the tube wall to move outwardly against the surfaces of tube sheet apertures 44, thus locking the tubes to the tube sheet 18. Additionally, the four endmost tubes are caused to be locked against the surfaces of baflle flange openings 46. The tubes are thus locked to the tube sheet 18 and baflie sheets 22 and 24 as a rigid construction; this is accomplished without extraneous bolts, rivets, adhesives or the like.

Movement of the mandrels through the tubes expands the tubes against the fin collars 42, thus locking the fins onto the tubes (for improved heat transfer). The final portion of the mandrel stroke locks the respective tubes to tube sheet 20 and the adjacent baffle flanges 36. Preferably the expansion operation is a single stroke process. It is believed that hydraulic expansion can be used in lieu of mechanical expansion.

During the tube expansion process the outward radial movement of the tube wall draws the tube materially axially. As a result, the tube tends to elongate slightly, about 2% in a typical situation. Because of this elongation factor it is desirable during the expansion process to avoid any restrainment on the baflle sheets or fins. The baflle sheets and fins should be in a free-floating condition without applied stress, as from fixed guide or support structures.

FIG. 4 illustrates an arrangement in which the baffle sheet flanges 36 lie against the outer faces of the tube sheets. It is possible of course to size the parts so that the baffle sheet flanges lie against the inner faces of the tube sheets. The tubes used in the FIG. 1 arrangement are U-shaped, but it is of course possible to use straight open-ended tubes if desired.

Difierentiation over prior art practice It is old to form heat exchangers to include rectangular framework structures, and to connect the fluid tubes thereto by running expander tools through the tube interiors. What is new is my use of baflle sheet flanges 36 equipped with openings 46 which telescope onto the endmost fluid tubes; it is this arrangement which causes the framework components to be rigidly connected together as a part of the process of locking the tubes onto the fins and the tube sheets. The fluid tubes are of larger diameter, e.g., /s inch, than connector screws or bolts, so that the instant connections are more rigid and permanent than the corresponding prior art connections.

Preferably the openings 44 and 46 in the tube sheet flanges and baflle flanges are circular openings completely enclosed by the flange material, i.e., the edge of each opening is endless. It is contemplated however that certain ones of the openings could be U-shaped slots or cut-outs in an edge of each flange. In that event the tube would grip the edge of the flange opening for over one hundred eighty radial degrees, suflicient in many cases to form a locked connection of adequate strength.

I claim:

1. A heat exchanger comprising two spaced parallel apertured tube sheets; a plurality of fluid tubes extending through the apertures in said sheets; heat exchange fins having gripping engagement with the tubes in the space between the sheets; and two bafiie sheets interconnecting the corresponding ends of the tube sheets to cooperate therewith in forming a rectangular framework; each bafile sheet having flanges at'the ends thereof which connect with the respective tube sheets; each flange being turned onto a face of the tube sheet and being provided with an opening aligning with one of the sheet apertures; selected ones of the tubes having gripping engagement with the surfaces of the flange openings and aligned apertures, whereby to lock the baffles and tube sheets together for defining a rigid framework; said selected tubes constituting the sole means for connecting the tube sheets with the bafiie sheet flanges.

4 2. The heat exchanger of claim 1 wherein each flange engages the outer face of a tube sheet.

3. The heat exchanger of claim 1 wherein the fins are equipped with collars telescoped onto the fluid tubes; said tubes having gripping engagement with the collars.

References Cited UNITED STATES PATENTS 1,377,912 5/1921 Nebel 165--15l 1,735,807 11/1929 Swank 165149 3,246,691 4/1966 LaPorte et al. 165-151 FOREIGN PATENTS 202,794 10/ 1908 Germany. 724,017 2/1955 Great Britain.

MILTON KAUFMAN, Primary Examiner.

MANUEL ANTONAKAS, Assistant Examiner.

US. Cl. X.R. 

